Spatial differentiation mechanism of Non-LIPs Hg source-sink processes in the Early Cambrian Yangtze Platform, South China

Early Cambrian mercury (Hg) anomalies in Non-Large Igneous Provinces (Non-LIPs) on the Yangtze Platform reveal how deep Earth processes influenced surface environments during the Ediacaran-Cambrian transition. Geochemical data—including total organic carbon (TOC), total sulfur (TS), and Hg contents—from marine shales of the Lower Cambrian of South China show that submarine hydrothermal systems—not volcanic or atmospheric inputs—were the primary Hg source. Regional extension triggered shallow magmatism and thermal circulation; Hg-enriched fluids entered the ocean through deep faults. Paleo-upwelling transported Hg from deep hydrothermal zones to shallow areas. Seawater sulfate ([SO₄^2-]_sw) controlled Hg burial: in shallow settings, high [SO₄^2-] promoted bacterial sulfate reduction (BSR), enabling Hg to bind to both organic matter (OM) and sulfides; in deep basins, low [SO₄^2-] limited sulfide formation, favoring Hg-OM complexes; near hydrothermal vents, thermochemical sulfate reduction (TSR) generated H₂S, restoring Hg-sulfide burial. These spatial patterns link biogeochemical cycles to tectonic activity. Hydrothermal H₂S also modulated ocean redox conditions, potentially creating stable habitats for early animals and driving biological innovation. Thus, Non-LIP Hg dynamics reflect deep-surface coupling and illuminate life-Earth co-evolution during this critical transition.